Protein kinases, the largest family of human enzymes, encompass well over 500 proteins. Spleen Tyrosine Kinase (Syk) is a member of the Syk family of tyrosine kinases, and is a regulator of early B-cell development as well as mature B-cell activation, signaling, and survival.
The inhibition of Syk activity can be useful for the treatment of allergic disorders, autoimmune diseases and inflammatory diseases such as: SLE, rheumatoid arthritis, multiple vasculitides, idiopathic thrombocytopenic purpura (ITP), myasthenia gravis, allergic rhinitis, chronic obstructive pulmonary disease (COPD), adult respiratory distress syndrome (ARDs) and asthma. In addition, Syk has been reported to play an important role in ligand-independent tonic signaling through the B-cell receptor, known to be an important survival signal in B-cells. Thus, inhibition of Syk activity may also be useful in treating certain types of cancer, including B-cell lymphoma and leukemia. U.S. Pat. Nos. 8,455,493 and 8,440,667 disclose Syk inhibitors, the disclosures of which are hereby incorporated by reference in their entirety.
There is a continued need to provide compounds that are effective Syk inhibitors, including compounds having desirable pharmacokinetic properties for use as therapeutics for treating cancers and other diseases.